Silica-aluminum

If the materials of interest are adsorbed on the surface of the solid impurities by polar forces, for example, due to contamination by substances such as silica, aluminum silicate or metal oxide, then they... 

Formation permeability damage caused by precipitation of dissolved minerals such as colloidal silica, aluminum hydroxide, and aluminum fluoride can reduce the benefits of acidizing (132-134). Careful treatment design, particularly in the concentration and amount of HF used is needed to minimize this problem. Hydrofluoric acid initially reacts with clays and feldspars to form silicon and aluminum fluorides. These species can react with additional clays and feldspars depositing hydrated silica in rock flow channels (106). This usually occurs before the spent acid can be recovered from the formation. However, some workers have concluded that permeability damage due to silica precipitation is much less than previously thought (135). 

We assume a 0.1 molal KC1 solution containing hypothetical amounts of silica, aluminum, and carbonate. We set temperature to 200 °C and run the calculation... 

High-silica, aluminum-deficient zeolites have been prepared by the following methods (Table I) ... 

The secret that makes this process work is no surprise, the catalyst. Those that work include some of the noble metals, specifically, platinum or palladium, a rare earth metal like cerium or neodynium (are they rare or what ) on alumina, or a non-noble metal like chromium on a silica-aluminum support. 

The fifth and final adsorbent characteristic is zeolite type. The adsorbent used in the Molex process is a proprietary and is a particularly effective adsorbent for normal paraffin separation [4, 5] and has achieved purity and recovery targets for the Molex processes. A sampUng of various molecules (and their corresponding dimensions) that Molex can easily separate is listed in Table 8.1. As discussed in Chapter 6, a zeoUtes s pore structure is dependent on its silica aluminum ratio and the proprietary Molex adsorbent possess a uniform repeating three-dimensional porous structure with pores running perpendicular to each other in the x. 

Aluminum nitride from bauxite, carbon and nitrogen (17), and the formation of silica-aluminum-nitride mixtures from various clays at about 1500°C. and higher temperatures. 

Ozone applications in gas/water/solid systems cover a wide range of media such as sludges, soils, adsorbents and catalysts. Disinfection, which can be regarded as a three-phase system, is a well-described and established application (see Section A 3.2.1 and 3.3.2). The preozonation for particle removal is discussed frequently, especially in the treatment of surface water, where different organic (e. g. bacteria, viruses, algae, suspended organic matter) and inorganic (e. g. silica, aluminum and iron oxides, clay) particles can be present (see Section A 3.2.4). 

R.M. Barrer and T. Gabor, Sorption and Diffusion of Simple Gases in Silica-Aluminum Cracking Catalyst, Proc. R. Soc. London, Ser. A 265, 267 (1960). 

Ikeda, T., Sasaki, M., Hachiya, K., Astumian, R, D., Yasunaga, T., and Schelly, Z. A. (1982b). Adsorption-desorption kinetics of acetic acid on silica-aluminum particles in aqueous suspensions, using p-jump relaxation method. J. Phys. Chem. 86, 3861-3866. 

Lewis Acid Sites. Many other mechanisms (66, 85) are best described in terms of the more general concept of aprotic, or Lewis acidity which is defined in terms of the capacity to donate or share pairs of electrons. Aprotic acid sites are commonly derived from the coordinatively unsaturated cations at crystal edges or adsorbed on crystal faces, from deydration of hydroxylated surfaces, and from deamination or deamination and dehydration of silica-aluminum catalysts or similarly treated clays having extensive tetrahedral substitution (130, 132). Formation of Lewis acid sites by deamination or deamination-dehydration is dependent on inversion of the basal oxygens of the aluminum-substituted tetrahedron away from the surface, in order to expose the aluminum (131). 

Combinations of cationic starch and anionic microparticles are useful commercial systems. Shear-sensitive flocculation occurs, allowing microscale reflocculation in the formed paper sheet, which improves dewatering and retention.63,75,76 The microparticles can be colloidal silica, aluminum silicate, poly(silicic acid) or bentonite of specific size and surface area.77 79 Cationic, anionic or polymeric aluminum-containing compounds can be additional components. A three-part coacervate system uses a high molecular weight anionic polyacrylamide, cationic starch and silica.80 Cooking cationic starch in the presence of an anionic silica hydrosol was reported to improve drainage and retention.81... 

It is, however, more complex than this because the silica-alumina support affects also the polymerization. A. Clark describes the correlation between the chromium trioxide and the silica-aluminum support. He also shows the effect of the catalyst activation temperature on the molecular weight of the polyethylene formed. 

The catalyst may be prepared by impregnating a silica-aluminum support with an aqueous solution of chromium trioxide. After drying, the catalyst is usually activated in a stream of dry air at temperatures ranging from ca. 400°-800°C. Under these conditions catalysts can be prepared with a major percentage of chromium in the form of chromium trioxide. Evidently, the support is not just an inert diluent for chromium oxide by itself is stable only as Cr203 at these temperatures. There must be interaction between chromium trioxide and the support which stabilizes the former. 

Particularly attractive method for preparation of synthetic zeolite is recrystallization of natural aluminosilicates, such as kaolinite (halloysite), previously formed for elimination of plastic flow of highly thixotropic, pulverized zeolite. Some additional components of initial mixtures, such as texture modifiers (hard coal, lignite, cellulose, silica, aluminum oxide) are also introduced. They enrich the structure of zeolite adsorbent in transport pores and prevent an excessive compression of the clay material during the formation process. This results in an increase in product efficiency during the crystallization of zeolite phase. 

Fig. 2. H2O adsorption isotherms of silica, aluminum silicate and titanium silicate-impregnated ceramic sheets.

Explain the following statements (from Morel and Hering, 1993). For example, silica, aluminum oxide (gibbsite), and kaolinite cannot coexist at equilibrium ... 

Typical fillers carbon fiber, glass fiber, graphite lubricant for wear resistant applications molybdenum sulfide, PTFE. antimony trioxide, barium titanate, clay, silica, aluminum nitride, smectite... 

Typical fillers firmed silica, calcium carbonate, carbon black, silver, glass beads, metal powders, precipitated silica, aluminum oxide, montmorillonite. mica, zinc oxide... 

A complication in doping experiments with silica is that the state of the impurity (A13+) may depend on the presence of other impurities. In quartz and fused silica, aluminum can be put in a substitutional position only if a charge-compensating cation such as Na+ is also present (86). If this is also true for silica gel, then the concentration of color that can be produced in a given sample will depend on the concentrations of both aluminum and some monovalent cation. 

In the formation of valuable oxygen-containing compounds by the controlled or partial oxidation of hydrocarbons, such as benzene, two factors are of great importance, i.e., temperature and type of catahst. Other factors such as composition of hydrocarbon-air mixture and time of contact are also important. All of these factors are intimately related to each other and the successful operation of the process depends upon the control of each of them. It was early found that if mixtures of benzene apor and air in excess of tliat necessary for complete combustion were passed through heated tubes of such non-catalytic materials as iron, silica, aluminum, etc., and the temperature allowed to rise at will, only complete combustion products could be obtained, and no intermediate oxidation products could be isolated. On the other hand, if such mixtures of benzene vapor and air were passed over a catalyst such as platinum black, complete combustion also occurred but at a temperature far below that necessary in the empty tube made of non-catalytic material. However, only very small amounts of intermediate products could be obtained with such an active catalyst even when the temperatures were carefully controlled or the time of contact made very short. It is difficult to form any definite idea as to the temperatures which were actually attained by the reacting gases in most of the early experiments reported in the literature. Lack of uniformity in construction of reaction chambers, in displacement of cata-... 

In a previous paper (Anderson and Benjamin accepted for publication in Environmental Science and Technology), surface and bulk characteristics of amorphous oxides of silica, aluminum, and iron, both singly and in binary mixtures were described. The solids were characterized with an array of complementary analytical and experimental techniques, including scanning electron microscopy, particle size distribution, x-ray photoelectron spectroscopy (XPS),... 

Because of high titanium concentrations in soils and the widespread use of titanium oxide as a pigment, the toxicity of titanium oxide to animals has been the subject of much investigation. The results show that titanium oxide is not toxic. Intratracheal administration of ilmenite to rats led to slight fibrogenicity, due to the silica, aluminum oxide and iron oxide contents of the titanium concentrate. Likewise, a small... 

Thomas and Birchall [101,102] studied the concentration of ions OH, calcium, silica, aluminum and iron in the solution (w/c=2) of cement slurries with additions... 

Earlier, Mikhailenko et al. have introduced boron orthophosphate (BPO4) as an inorganic material (Mikhailenko et al. 1998). The composite SPEEK/BPO4 was able to increase the proton conductivity as the water uptake was also increased. There were no reported data on methanol permeability, but it was mentioned that the porosity of the membrane was increased. This chapter continues with more details on the SPEEK modification by using various types of inorganics such as Cloisite 15A, boron orthophosphate, and tungstosilicic acid supported on silica-aluminum oxide. 

TLC HPTIjC plates Silica—aluminum T JC CHa3/MeOH/0.2% CaClj (55 45 10, THAP Matrix mixtures MALDI/FT-MS Ganglioside mixtures [39] ... 

Fused-silica aluminum oxide ALOT column 30 m x 0.32 mm oven temperature 60 °C detector FID split ratio, split injection 1 25 of 20 nl gas mixture of Ci - 64 hydrocarbons water equalizer. 

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